{{short description, Charged particle detector Spark chamber demonstration v2

A spark chamber is a

particle detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nu ...

: a device used in

particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

for detecting electrically charged

particles In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...

. They were most widely used as research tools from the 1930s to the 1960s and have since been superseded by other technologies such as drift chambers and

silicon detector A semiconductor detector in ionizing radiation detection physics is a device that uses a semiconductor (usually silicon or germanium) to measure the effect of incident charged particles or photons. Semiconductor detectors find broad applicati ...

s. Today, working spark chambers are mostly found in science museums and educational organisations, where they are used to demonstrate aspects of particle physics and astrophysics. Spark chambers consist of a stack of metal plates placed in a sealed box filled with a gas such as

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

, neon or a mixture of the two. When a charged particle from a cosmic ray travels through the box, it

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

ises the gas between the plates. Ordinarily this ionisation would remain invisible. However, if a high enough

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

can be applied between each adjacent pair of plates before that ionisation disappears, then sparks can be made to form along the trajectory taken by the ray, and the cosmic ray in effect becomes visible as a line of sparks. In order to control when this voltage is applied, a separate detector (often containing a pair of scintillators placed above and below the box) is needed. When this trigger senses that a cosmic ray has just passed, it fires a fast switch to connect the high voltage to the plates. The high voltage cannot be connected to the plates permanently, as this would lead to arc formation and continuous discharging.

As research devices, spark chamber detectors have lower resolution than

bubble chamber A bubble chamber is a vessel filled with a superheated transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded the 1 ...

detectors. However they can be made highly selective with the help of auxiliary detectors, making them useful in searching for very rare events.

Related devices

A streamer chamber is a type of detector closely related to the spark chamber. In a spark chamber one looks at a stack of parallel plates edge-on. For this reason, best viewing is afforded when the particle comes in perpendicularly to the plates. A streamer chamber, in contrast, typically has only two plates, at least one of which is transparent (e.g. wire mesh or a conductive glass). Particles come in roughly parallel to the plane of these plates. A much shorter high-voltage pulse is used than with a spark chamber, so there is insufficient time for sparks to form. Instead very dim streamers of ionised gas are formed. These can be seen when image enhancement is applied.

External links

University of Cambridge Spark Chambers

"How does a spark chamber work?" - From an exhibitor at the 2011 Royal Society Summer Science Exhibition.

Enhanced image of streamers taken in a steamer chamber
Particle detectors

Related devices

See also

External links